// Copyright 2024 E99p1ant. All rights reserved.
// Use of this source code is governed by a MIT-style
// license that can be found in the LICENSE file.

package pixel

import (
	"io"
	"net/http"
	"path"
	"strconv"
	"strings"
	"time"

	"github.com/sirupsen/logrus"

	"github.com/tamakyi/TamaBox/internal/conf"
	"github.com/tamakyi/TamaBox/internal/context"
	"github.com/tamakyi/TamaBox/internal/i18n"
)

// pixelSafeResponseHeaders 允许从上游透传到客户端的响应头白名单。
// 绝不透传 Set-Cookie / Set-Cookie2 等，避免上游借像素代理向客户端注入会话或凭证。
var pixelSafeResponseHeaders = []string{
	"Content-Type",
	"Content-Length",
	"Content-Encoding",
	"Content-Disposition",
	"Cache-Control",
	"ETag",
	"Expires",
	"Last-Modified",
	"Pragma",
	"Vary",
}

func Index(ctx context.Context) {
	ctx.Success("pixel")
}

func Proxy(ctx context.Context) error {
	uri := ctx.Param("**")

	// 路径穿越防护：归一化后必须仍位于 /api/ 之下，
	// 否则（如含 ../ 跳出 /api）直接拒绝，防止访问到未授权路径。
	cleaned := path.Clean("/api/" + uri)
	if !strings.HasPrefix(cleaned, "/api/") {
		return ctx.JSONError(http.StatusBadRequest, i18n.T(ctx.Lang(), "pixel.errPath"))
	}

	userID := strconv.Itoa(int(ctx.User.ID))

	// 仅允许只读 GET：写方法（POST/PUT/DELETE）在路由层已被限制为 GET，
	// 此处不再处理请求体，杜绝被用作对上游的越权写入口。
	req, err := http.NewRequest(http.MethodGet, "http://pixel/", nil)
	if err != nil {
		logrus.WithContext(ctx.Request().Context()).WithError(err).Error("Failed to create request")
		return ctx.ServerError()
	}
	req.URL.Host = conf.Pixel.Host
	req.URL.Path = cleaned
	req.Header.Set("neko-user-id", userID)

	client := http.Client{Timeout: 10 * time.Second}
	resp, err := client.Do(req)
	if err != nil {
		logrus.WithContext(ctx.Request().Context()).WithError(err).Error("Failed to send request")
		return ctx.ServerError()
	}
	defer func() { _ = resp.Body.Close() }()

	// 仅透传白名单内的安全响应头。
	for _, k := range pixelSafeResponseHeaders {
		if v := resp.Header.Get(k); v != "" {
			ctx.ResponseWriter().Header().Set(k, v)
		}
	}
	ctx.ResponseWriter().WriteHeader(resp.StatusCode)

	_, err = io.Copy(ctx.ResponseWriter(), resp.Body)
	if err != nil {
		logrus.WithContext(ctx.Request().Context()).WithError(err).Error("Failed to copy response")
		return ctx.ServerError()
	}

	return nil
}